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From Jeff Trawick <traw...@gmail.com>
Subject Re: [users@httpd] MaxRequestsPerChild - New child process doesn't process requests
Date Fri, 22 Aug 2014 11:42:51 GMT
On Fri, Aug 22, 2014 at 3:46 AM, Vattikuti, Vamsi Krishna Venkata (STSD) <
vamsik@hp.com> wrote:

>  Hi,
>
>
>
> Thanks for the feedback.
>
>
>
> That tomcat application(monitoring) is invoked through a 3rd party module
> and  application remains active in browser for days together, which result
> in memory leak for httpd process. To prevent that leak, that application
> owner has configured MaxRequestsPerChild as 100. I will suggest them to
> increase values of this and other directives.
>

It is likely that you won't find a satisfactory solution as long as you
have memory leaks in httpd and extremely-long-running requests.  The leak
needs to be fixed.

I think you will be better off with the prefork MPM until this can be fixed:

* Since you have such a low MaxClients, you're not getting much benefit
from the worker MPM.
* When a prefork child process reaches MaxRequestsPerChild, it can exit
immediately since there are no other active requests in the child process,
and not be stranded forever, consuming resources but not able to accept new
connections.
* If necessary, a person or a monitoring script can kill individual prefork
child processes based on time of active request or memory use, and only
affect a single active request.

If this third-party module also requires exactly one child process, in
addition to leaking memory and requiring child process cleanup, you've hit
double jeopardy.  Switch to another line of work.


>
> Regards,
>
> Vamsi.
>
>
>
> *From:* Daniel [mailto:dferradal@gmail.com]
> *Sent:* Friday, August 22, 2014 12:50 PM
>
> *To:* users@httpd.apache.org
> *Subject:* Re: [users@httpd] MaxRequestsPerChild - New child process
> doesn't process requests
>
>
>
> What memory leak exactly? You are just proxying to tomcat.
>
>
>
> Increase the number of maxrequestsperchild to a more sensible number, such
> as 10.000 or even higher, so httpd is not constantly renewing childs if you
> have even a minimum load.
>
>
>
> Add more servers to avoid your issue, and try to use more threads too, 50
> at least.
>
>
>
> It seems like you are constraining too much, and apache 2.2.15 with
> mpm_worker can give much much more.
>
>
>
> You will notice performance increasing greatly overall.
>
>
>
>
>
>
>
> 2014-08-22 6:06 GMT+02:00 Vattikuti, Vamsi Krishna Venkata (STSD) <
> vamsik@hp.com>:
>
>  Hi Jeff,
>
>
>
> Thanks for quick response. We will check and do the needful
>
>
>
> That 100 is to prevent memory leak.
>
>
>
> Regards,
>
> Krishna.
>
>
>
> *From:* Jeff Trawick [mailto:trawick@gmail.com]
> *Sent:* Friday, August 22, 2014 2:24 AM
> *To:* users@httpd.apache.org
> *Subject:* Re: [users@httpd] MaxRequestsPerChild - New child process
> doesn't process requests
>
>
>
> On Thu, Aug 21, 2014 at 4:39 PM, Vattikuti, Vamsi Krishna Venkata (STSD) <
> vamsik@hp.com> wrote:
>
>  Hi,
>
>
>
> We are having an issue with Tomcat application accessing through proxy and
> details are below. Can you please check and share your feedback.
>
>
>
> *Issue:*
>
> We have an application(tomcat) accessed through proxy as below. Also, we
> have MaxRequestsPerChild setting as 100
>
>
>
> Whenever MaxRequestsPerChild reached its limit, a new process is started
> but the application become unresponsive. It seems that new process doesn’t
> service any requests
>
> We have to restart httpd to recover that
>
>
>
>
>
> *Log:*
>
> -          Access.log doesn’t show any requests for new child
>
> -          Error_log shows that
>
> a)      workers are initiated for new process but it didn’t service any
> requests
>
> b)
>
> c)       processing has stuck for a minute due to some reason
>
>    [Fri Aug 08 16:09:17 2014] [debug] ssl_engine_kernel.c(2118): [client
> 127.0.0.1] Certificate Verification, depth 0 [subject:
> /C=y/ST=y/L=y/O=y/OU=y/CN=y, issuer: /C=y/ST=y/L=y/O=y/OU=y/CN=y, serial:
> xyz]
>
>    [Fri Aug 08 16:10:12 2014] [info] [client 10.150.90.25] Connection to
> child 6 established (server *:<port number from client>)
>
>
>
> d)      SSL handshake has started but didn’t complete for 4 connections
> related to new process. There are no errors related to ssl
>
> $ grep -i handshake errorlog.2014-08-08-07_06_44 | grep -c start
>
> 707
>
> $ grep -i handshake errorlog.2014-08-08-07_06_44 | grep -c done
>
> 703
>
> $
>
>
>
> *Apache version:*
>
> 2.2.15
>
>
>
>
>
> *Proxy setting:*
>
> SSLProxyEngine On
>
> SSLProxyCipherSuite ALL
>
> SSLProxyMachineCertificateFile /var/ssl/proxy.pem
>
>
>
> proxyPass /app1 https://localhost:<port number>/app1 (Tomcat)
>
>
>
> *Worker configuration:*
>
> KeepAlive On
>
> MaxKeepAliveRequests 100
>
> KeepAliveTimeout 15
>
> <IfModule worker.c>
>
> StartServers         1
>
> MaxClients           25
>
> MinSpareThreads      12
>
> MaxSpareThreads      25
>
> ThreadsPerChild      25
>
> ServerLimit          1
>
> MaxRequestsPerChild  100
>
> MaxMemFree  50
>
> </IfModule>
>
>
>
> Thanks & Regards,
>
> Krishna
>
>
> MaxRequestsPerChild 100 is ridiculously low.  What is happening in httpd
> to cause you to need that setting?
>
>
>
> Anyway...
>
>
>
> Once an httpd child process has reached 100 connections, it initiates a
> graceful shutdown, which means that instead of aborting current requests it
> will instead wait for current requests to finish, then exit.
>
>
>
> During the time that it is waiting for current requests to finish, new
> connections must be handled by other child processes.  BUT you set
> ServerLimit to 1 (and other directives such as ThreadsPerChild and
> MaxClients are consistent with allowing only one child process), so no
> other child process can be created during that time.
>
>
>
> Thus, once 100 connections are handled, new clients will be blocked until
> existing requests finish.
>
>
>
> --/--
>
>
>
> My guess:  Your Java application takes a long time (maybe forever?) to
> handle some requests.  MaxRequestsPerChild makes it worse.  If the Java
> requests are slow and eventually finish, the solution is to keep a steady
> set of httpd child processes (having them gracefully exit when there are
> slow backend requests can be harmful) and increase the number of httpd
> threads/child processes to handle the load.
>
>
>
> If some Java requests hang, see how to handle that on the Tomcat side.
>
>
>  Enable server status with ExtendedStatus On and watch what happens --
> whether or not certain requests handled by the Java application take a
> relatively long time, tieing up some or all of your very limited number of
> httpd threads.
>
>
>
> --
>
> Born in Roswell... married an alien...
> http://emptyhammock.com/
>
>
>
>
>



-- 
Born in Roswell... married an alien...
http://emptyhammock.com/

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